Power transmission mechanism



Patented Oct. 18, 1932.

UNITED- STATES- PA E-Nr OFFICE.

ALBERT A. DENSMORE, OF BOSTOlN', MASSACHUSETTS, ASSIGNOR TO ECLIPSE MACHINE COMPANY, OF ELMIRA HEIGHTS, NEW JERSEY, A CORPORATION OF NEW YORK 'rownn TRANSMISSION- mncmmsm Application filed June 10,

This invention concerns power transmission mechanism and relates more particuconnections however. being adapted larly to engine starting devices.

The usual type of electrically driven start er for internal combustion engines comprises a pinion which is driven by the armature shaft and which is automatically moved into and out of mesh with a gear carried by the engine shaft. In some installations the pin ion is provided with means intended to pre-- vent its rotation with the armature shaft prior to its engagement with the engine gear, but in practice such means are sometimes found inadequate, due for example to the accumulation of dirt, gummy oil, etc. upon the engaging parts, so that the pinion may be caused while rotating at high velocity to approach and contact with the gear, thus producing a disagreeable noise or may fail to traverse into engagement with tlie gear until the actuation of the starting motor is repeated.

The ordinary starter moreover is limited with respect to the capacity of the drive for yielding'under overload. When, therefore, as may happen through carelessness on the partof the operator or for other reason, the

engine back fires in starting, the automatic.

starting mechanism is thereby subjected to heavy stresses which may be objectionable.

Objects of the present invention are toprovide a starter of a type of such character as to assure lntermeshing of the plnion with the engine gear prlor to rotation of the pinion, and under substantially all condi-' tions of use, and also to provide connections between the starting motor and pinion of a character such as to permit reverse rotat'on of the pinion relatively to the armature shaft under extraordinary conditions, such for example as back firing of theen ine, the under ordinary circumstances to transmit movement of the armature shaft to the pinion for starting the engine in the proper direction.

For attaining the above objects, a screw clutch is preferably employed, such clutch comprising cooperating threaded parts to one of which the drive pinion is connected,

and relative rotation of which the pinion 1922. Serial inseam.

is caused tomove'axially into mesh with the engine gear prior to its rotation with the other of said parts by the armature shaft.

For producing such relative rotation of the I .55

tion when subjected to suflicient turning force. Preferably such connections comprise a cam element and a second element normally engaging the same but having no positive connection thereto, together with a. spring for opposing relative movement of rotation of said elements. One of said elements is secured to the armature shaft and the other to the driving art of 'the screw clutch,the spring being 0 suflicient strength to insure transmission of the 'normal'driving from. one of said elements to the other while permitting reverse movement of the driven element relatively to the drive element upon application of s'ufiicient force, as for example, in back firing of the engine.

In one form of the device the engaging elements comprise complement-a1 cam surfaces force carried by the opposed end faces of a pair i of aligned, cylindrical blocks, one of such blocks being secured to the armature shaft and the other being carried by a sleeve constituting the driving member of a screw clutch. The latter block is urged toward the first block by a heavy spring the tension of which may be adjusted, so that relative turning of the complemental cam elements is lim vations of the cam surfaces are passed relieving the spring of such tension, suchincrease and decreasejn tension being repeated until the energy of back fire has ceased whereupon the armature shaft automatically picks up the driven element ready'for a new attempt, at starting. Thus the starter may operate continuously irrespective of back firing and without danger of breakage or injury of parts. While it is contemplated that.

some of the advantages of the present device might be secured by the use of a shear pin between certain of the driving connections and which would, upon back firing, be sheared off, thus avoiding breakage of moge important and costly elements, such an arrangement necessitates some delay at least, and is regarded as decidedly inferior to the arrangement above referred to. While spring controlled cam elements are very efficacious in attaining the results wished for, it is contemplated that other and equivalent means may well be employed for attaining the desired objects, it being regarded however, as very desirable that the driving means involve entirely independent elements having no positive connection so that while normally operative to turn simultaneously in the same direction, one may turn to any requisite amount in a reverse direction without breakg parts or necessarily stopping or reversing the other.

In order to avoid any possibility of the pinion partaking of the rotation of the armature shaft prior to its engagement with the engine gear it is preferred to employ a device of a coil compression spring. In the inoperatlve position of the parts this spring is under maximumcompression, but as the pinion is moved axially toward the engine gear by the screw clutch device the force of the spring gradually diminishes until at the instant the pinion fully meshes with the gear, the braking effect of the disk is substantially eliminated It is thus evident thatat the' instant of starting of the armature shaft the pinion is most strongly held against rotation so that any accumulation of dirt or gum between the pinion and its driving element such as would tend to carry the pinion with the driving element as the latter rotates is rendered ineffective by the brake, while as the pinion assumes driving position it is substantially freed from contact with the brake' and thus during driving no substantial fric tional brake effect remains.

In the accompanying drawings there is illustrated by way of example an arrangement of parts well adapted .to secure the desired ob ects and in such drawings I Fig. 1 is a side elevatiompartly in vertical longitudinal section, of an engine starting mechanism of a'prefe'rred form, showing the parts in initial, inoperative position;

Fig. 2 is a side elevation of the device shown in Fig.1, the parts being shown, how-' ever, as in position for driving the engine gear;

Fig. 3 is a. view similar to Fig. 1, but illustrating a modification;

Fig. 4 is a view similar to Figol, but illustrating a further modification;

Fig. 5 is a fragmentary, longitudinal cross section, to somewhat larger scale than the preceding figures, and illustrating a still further modification;

Fig. 6 is a vertical cross section on the line 6-6 of Fig. 5; and

Fig. 7 is a plan view illustrating a detail of one of the elements of the device shown in Figs. 5 and 6.

Referring to Figs. 1 and 2, an internal combustion engine of any usual ty e is indicated at 1, such engine having a s aft provided with a fly wheel 2 having a spur gear 3 secured to or integral with its rim. It is to be understood, however, that such gear might, if desired, be mounted independently upon the engine shaft or might even be carried by a separate shaft driven from the engine. An electrically operated start ing motor 4 of usual type, is also shown, such motor having an armature shaft 5, and being mounted upon any suitable support. Secured to the shaft 5 is a yoke member or attaching collar 7 comprising a sleeve portion 8 into which the shaft extends and to which it is secured by means-of a pin 6. This sleeve portion is provided with an enlarged hub element 9 which is preferably provided with a square socket with which engages the square end 10 of a shaft 11 which aligns with, and is in eflect an extension of, the armature shaft 5. The opposite end of this shaft turnsin a bearing 12 provided in a. bracket 13 secured in any desired manner to the engine frame. A hollow shaft or sleeve 14 is mounted upon the shaft 11, turning freely thereon, such sleeve being provided with a radially projecting pin 16 engaging a circumferential groove upon. the inner surface of a cylindrical cam block 17. Thiscam block is externally screw-threaded, as indicated at 18, for engagement with internal screwthreads 19 upon the inner surface of the yoke member 7, the cam block being thus adjustable lon itudinally with respect to such yoke mem er. in adjusted position a set screw 20 may be provided. With the parts as thus arranged, it is clear that rotation of the armature shaft 5 will rotate the yoke 7 and the shaft'll and that rotation of the yoke will turn the cam block 17 which forms in efiect a rigid though adjustable part thereof. Rotation of the cam For holding the parts block however, is not directly transmittedto the sleeve 14, as the pin 16 moves freely in the groove 15, this groove, however, pro- .viding against relative longitudinal movement of the cam block and sleeve. A. second cam block 21 is also mounted .upon the sleeve stood, however, that any desired variation 1 in the respective cam faces may be employed such as may prove to give the best results under special conditions of use. The cam.

block 21 is provided at its right-hand end, as viewed in Fig. 1, with an annular flange 26 which defines a seat. for one end of a coil spring 27 which surrounds the sleeve "14. The sleeve 14 is externally screw threaded at its right-hand extremity (as viewed in Fig. 1) for engagement with screw threads upon the interiorsurface of a flanged abutment member or stop collar 28, such abutment member being, provided with an annular flange 29 defining a seat for the opposite end of the spring 27. The abutment member 28 is adjustable longitudinally of the sleeve 14 by its screw threaded connection therewith, but may be secured in adjusted position by means of a set screw 30 so as to form in effect a rigid part ofsaid member 14.

At its right-hand end the sleeve 14 is provided with an enlarged bore 31, the interior lit surface of which is screw threaded so that the threaded annular wall forms in effect a nut of collar portion of which collar28 is, in efiect, a circumferential extension. A pinion 32 ismounted to turn freely on the shaft 1.1, such pinion being provided with an extended hub 33 constituting a sleeve or hollow shaft'mounted upon the shaft 5 of the motor and being externally screw threaded for engagement with the screw threads upon the interior surface of the bore 31. The bore and the 'hub are of such relative lengths as j to permit a stop on the screw sleeve or hub 33 to be brought into contact with the end surface 34 of the abutment member 28 the side of the pinion here serving as such stop and, the pinion when in this position meshing with the gear 3 of the engine shaft.

Preferably a brake disk 35 is mounted upon the shaft 11 to slide freely thereon, and is held in frictional contact with I the end face of pinion 32 by means of a coil spring 36 interposed between such disk and a second disk 37 which contacts with the .bearing 12. The length and tension of the spring 36 are I so determined that when the pinion 32 has been brought into engagement with the surface 34 of the abutment, thespring is substantially relieved from all compressive stress and the brake disk 35 bears with little, if any pressure against the face of the pinion.

The operation of the'device thus described is substantially as follows, it being assumed that the parts normally occupy the position indicated in Fig. 1 and that the engine gear 3 is stationary. Upon starting the motor 4 the shaft 5, yoke 7 and cam block 17' are simu1- taneously rotated. The first effect of this is'to place the spring 27 under slight compression dueto theaxial reaction of the cam faces 24 and 25. Only a slight compression of the spring is at firstnecessary to cause the cam block 21 to rotate with the armature shaft, thus turning the sleeve 14 relatively to the hub of pinion32 and drawing such hub axially into the bore 31 until the pinion meshes with gear 3 and comes into contact with the abutment surface 34. During such movement, theaction of the brake disc 35 tendsto restrain the pinion 32 against rotation with the sleeve so that as the pinion approaches the gear the parts move into mesh smoothly and noiselessly and without any tendency to break the edges ofthe teeth of the gear or pinion. As no further axial movement of the pinion relatively to the sleeve is now possible th e pinion is compelled to take up the movementof rotation of the sleeve, the efiect of the brake disc 35 at the end of the axialmovement of the pinion becoming substantially nil. Turning of the pinion is, however, opposed by the inertia'of the engine partsand thus the cam block 17 may becaused to slip relatively to cam block .21. Such relative rotary movement of theseparts results in compressing the spring 27 to a'greater degree until finally the'resistance to further compression of the spring equals the force necessary to turn the cam block 21' whereupon the latter block turns synchronously with block 17 and'the pinion 32 acts to rotate the gear 23 for starting the engine. The parts continue to operate in this manner until the engine has picked up normal speed, whereupon the pinion is driven by engagement with gear 3 at a speed sufficiently greater than that of the sleeve 14 to cause the hub 33 to retreat from the bore 31, thereby disengaging the pinion 32 from the gear 3 and at the same time compressing the brake spring 36. The starting motor 4 is automatically stopped as soon as the pinion has been dis engaged by the usual means em loyed for such purposes, and which is not lierein disclosed. The spring 27, compressed while the starting load .is being carried, tends, when. the starting apparatus is relieved of such load, to move the cam block 21 back to position shown in Fig. 1 and thus to cam the blocks 21'and 17 to their normal relative position. Such restoration is not absolutelynecs essary, however, as when the starting motor is again actuated, the compressibility of the spring 27 serves in any case to determine the relative positionsof the cam faces24 and 25 at which rotation of the block 21 for driving pinion 3 shall be initiated.

and

- with the operation of the armature shaft 5.v

With the arrangement above described, if for any'reason, as for example as through carelessness on the part of the operator, the engine should back-fire while the pinion 32 is in mesh with the gear 33, the reverse rotation of the sleeve thereby occasioned may take place without in any manner interfering In such case, the first action is to move the cam faces 24 and 25 in" such direction as to compress the spring 27 somewhat more than the normal amount and possibly sufficient to permit the high points of the cam faces to pass each other, thereupon the spring im mediately snaps the cam block 21 back to startingposition, axially of the shaft, from which it is again moved by the relative reverse rotations of the armature shaft and the sleeve. This operation is repeated so long as the momentum imparted to the sleeve 14 by the back-firing action subsists, but after such momentum has been overcome, the armature shaft again operates the parts in normal fashion in a further attempt to start the engine. Thus, the back-firing has no substantial effect on the starting mechanism except momentarily to increase the compres sion of the spring 27 and the parts thus remain integral and unbroken and ready at all times-for a further attempt at starting.

In Fig. 3 ment previously described is illustrated. In this figure the numeral 41 indicates an engine having a fly wheel '42 provided with a gear 43;. The starting motor is indicated at 44, having the armature shaft 45, to which is secured the yoke member 46, this yoke member corresponding generally to the yoke member 7 previously referred to. Secured to this yoke member is a cam block 47 which may have screw threaded engagement there-. with if desired, this cam block cooperating with a second camblock 48, the two blocks being provided with cooperating, complemental inclined cam faces in a manner similar to those previously described These cam blocksare mounted upon a sleeve member 49, the block 47 being secured against Y axial movement by means of apin 50 engaging a" circumferential groove in the cam block. The cam block 48 is provided with an outstanding annular flange 48 at its end whi'chserves to define a seat for a coil spring 52 surrounding the sleeve 49 and having its other end seated within a flange 53 carried by an abutment member, 54. The abutment member 54 is adjustably secured to the sleeve 49, as by means of a set screw 55; In this case the opposite ends 56, 57 of the spring are secured respectively within openings in c the bloek48 and the abut-ment member 54,

so that any relative turning movement of the latter members places th'e'spring under torsional stress. The outer end of the sleeve 49 isinternally screw threaded for engag a modification of the arrange ment with an externally threaded sleeve member 58 constituting a hub for a pinion 59, the member 58 being freely slidable upon the shaft 45 of the starting motor. A brake disk 60 bears against the outer face of the pinion 59, such brake disk being actuated y a coil sprin 61 surrounding the armature shaft and hearing at its opposite end against a collar 62. This collar forms a fixed abutment for the spring, bearing against or forming an integral part of the bearing 62 in which the end of the armature shaft turns. The operation of the device just described is similar in general to that shown in the Figs. 1 and 2. WVhen the armature shaft 45 is rotated, the cam block 47 is turned thereby forcing the cam block 48 longitudinally of the shaft )lacing the spring 52 under compression and also under torsional stress. lVhen the spring has been compressed to a predetermined amount, further relative turning movement of the cam blocks is prevented and motion is transmitted until its resistance is sufiicient to overcome the inertia of the engine parts, whereupon the sleeve 49 and pinion 32 are rotated with the shaft 5, thus turning gear 3. When the engine has attained its normal speed, the pinion 59 rotates at a speed greater than that of the sleeve 49, and is thus backed out of the latter, removing the pinion from engagement with the engine gear. If during starting, the engine back-fires, the spring 52 is first placed under greater compressive and torsional strain until the high portions of the cam blocks pass each other whereupon the parts reassume the axial position of Fig. 3. If reverse rotation .under the momentum of back-fire continues, the spring will be recompressed and the action will be repeated as often as may be necessary; While it is preferred to use the engaging, relatively movable cam elements in this specific construction, somewhat similar results might be attained by omitting them, and fixing the end 56 of spring 52. directly to the yoke 46, the spring in such case being made of sufficient length and resiliency to care for the added compression of back-firing. I Such an arrangement however, would not permit unlimitedreversal of the pinion, as is the case when the cam members are employed.

In' Fig. 4 a further modification is illus}. trated in which the engine isshown at 71,

yoke member 77, the end of which may, if

desired, constitute one of the cam blocks, being beveled off or otherwise sha ed' to provide the desired cam surface. ithin this yoke is journalled a sleeve 78 which is secured against endwise movement relatively to the yokeby means of a pin-7 9 fixed in the sleeve and turning freely in a groove 80 in the yoke. .A cam block 81 is also mounted upon the sleeve, this block having an end face cooperating with the end face of the yoke and being secured against rotation relatively to the sleeve by means 'of a pin 82 engaging a longitudinal slot 83 in the sleeve. The cam block 81 is thus free to move longitudinally of the sleeve while turning therewith. The outer'extremity of the sleeve is provided with an integralshoulder or flange 84 and between such flange and the end of the cam block 81 a coil spring 85 is arranged, such spring surroundingthe sleeve and tending normally to force the cam block 81 toward the yoke 77. The sleeve 78 is provided with a bore 86 for the reception of a sleeve 87 mounted upon the armature shaft. This sleeve 87 is provided with an enlar ement 88 at its left-hand end, as viewed in ig. 4, such enlargement being externally screwthreaded as shown at 89 for engagement with internal threads 90 on the inner surface of the bore 86. A pinion 91 is-mounted on the sleeve-87, being secured thereto by means of a set screw 92. A brake disk 93 is arranged to engage the end of the sleeve 87, or the hub of the pinion, as may be most convenient, such member '93 being,

actuated by a coil compression spring 94 whose opposite end bears against a collar or flange upon the bearing 76. The member 93 thus constitutes a brake normally tending to prevent rotation of the inion9l. v The Operation of this device is su stantially like that of the device illustrated in Figs. 1 and 2.

In Figs. 5, 6 and 7 a still further modification is illustrated. In these figures, theengine is omitted, the startin motor being shown at 104, having the sha 105 to which a yokemember 106 is secured by means of a set screw 107 or in any other suitable manner.v The engine flywheel is shown at 108, having the gear 109. ,The yoke member 106' comprises the hub 110 and a substantially annular portion 111 provided with a bore 112 concentric with the armature shaft. The member 111 is provided with per ends of springs such as 116. The lower end of each spring 116 is received in a simias shown at 115, orming seats for the uplar seat or chamber in a cylindrical, pistonlike niember 117 slidable' within the inner ends of the bores. The inner end of each piston 117 is provided with an axially extending contact member 118, see Fig. 7. A sleeve 119 is 'mountedto turn freely upon the armature shaft, such sleeve at one end entering the bore 112 in the yoke member 106 where it is provided wih a plurality of cam surfaces 120, 120, 120 respectively cooperating with the several contact members 118. These cam surfaces are separated by the high points 121, 121, 121 respectively, and are of concave curvature and preferably symmetrical with respect to the axis of the shaft. In the normal position of the parts the. contact members 118 engage such cam surfaces substantially at their central points. The sleeve 119 is rovided with an internally screw threaded ore, indicated at 122, with which engages an externally screw threaded hub member 123 secured to a pinion 124. Suitable brake means the several contact members 118 to move along the cam surfaces with which they engage. The first effect of such movement is to place the springs 116 under slight compression thereby turning the sleeve 119 and drawin the pinion 124 axially into engagement with the gear 109. As soon as the pinion 124 has been drawn into enga ement with the gear.109 further rotation oftfie sleeve 119 is opposed by the inertia of the engine parts' As the armature shaft 105 continues to rotate the springs 116 are now placed under greater compression until the compressive stress balances the inertia of the engine parts whereupon the latter are driven by the armature shaft for .turns the yoke member 106, thereby causing from the sleeve 117 in the manner described with respect to previous arrangements. WYhen the starting motor is stopped, the reaction of the contact members 118 upon the several cam surfaces 121, etc., tendsto restore the parts to the position of Fig. 5, although full restoration of the parts is not es sential. If during starting, the engine backfires, the only efi'ect-isto cause abnormal compression of the springs 116 such as to permit the contact members 118 to pass over the high points' 121, etc., of the sleeve member, thus Vhil the mechanism herein disclosed is particularly adapted for use in engine starters, it is contemplated that it may be useful in other situations where it is desired to-transmit power from one element to another, and

, particularly where it is possible that for some reason or other the driven element may be caused inadvertently to move in a reverse direction with force sufficient to break the driving connections if of ordinary construction.

It is also contemplated that other and additional variations and modifications of the fundamental features of the invention herein disclosed may be employed from time to time without departing from the spirit of the present invention.

I claim:

1. A power transmission mechanism for engine startin comprising a power,shaft, a sleeve co-axia therewith, cooperating cam elements carried by the shaft and sleeve respectively for transmitting motion of rotation from the former to the latter .and arranged to slip by each other in the event of an abnormal amount of torque being transmitted to thereby operatively disconnect the shaft and sleeve, a spring means normally operative to determine the driving pressure between said elements, a screw shaft concen-' trio with the sleeve and having screw threaded engagement therewith, said screw shaft having a driving member movable axlally therewith to engage a member of the engine to be started.

2. A mechanism of the class described comprising a rotatable shaft, a pinion mounted thereon for longitudinal movement thereof to engage a member of the engine to be started and for'rotary movement therewith, a source of power, and operating connections located between the pinion and source of power and consisting of two cooperating cam members, the first one of which is mounted on the shaft to rotate independently thereof but restrained against longitudinal movement thereon, and thesecond one of which is mounted on the ,shaft for positive rotary movement therewith and forlongitudinal movement thereon, a coiled spring encircling said shaft and cooperating with the second cam'member to hold it in engagement with the first cam member, and an adjustable collar arranged on the shaft} and serving on one side as an abutment for the pinion and on the otherside as an abutment for the spring.

ZnAhpower tIaII-SIIIISSlOIL mechanism compglsing' a driving member and a driven memr, one of said members having a cam elesurface and the other having an element engageable with said surface, said cam surface and element transmitting all the driving torque that is delivered from the driving member to the driven member, and spring means normally operative to retain said surface and element in driving engagement.

5. A power transmission mechanism comprising a driving member and a coaxial driven member, one of said members having an inclined cam face, and the other having an element engageable with said face, said cam sur face and element transmitting all the driving torque that is delivered from the driving members to the driven member, and adjustable spring means normally operative to r"- tain said cam face and said element in driving engagement. I

6. A transmission mechanism for engine starting comprising a power shaft, a sleeve coaxial therewith, .a cam block rotating with the shaft, a second and axially movable block mounted upon the sleeve and connected for and a torsion spring interposed between and connected to said flange and the axially movable block, respectively. v r

8. A-rpower transmission mechanism for en'- gine starting comprising a power shaft, a sleeve mounted freely thereon, a cam block rotating with the shaft, a second cam block splined to the sleeve and axially movable, said blocks having cooperable cam faces, a flange member mounted upon the sleeve and having threaded engagement therewith for adjustment axially therealong, and a coil compression spring encircling said sleeve'and interposed between said flange and the axially movable cam block.

9. A power transmission mechanism for engine starting comprising an armature shaft, a cam block fixed thereon, sleeve freely mounted upon the shaft,ia second cam block splined to the sleeve forrelative axial move-- ment but for rotation with the sleeve, said cam blocks having engaging, complemental cam faces, an ad ustable abutment upon the sleeve, a driving spring interposed between said abutment and the second cam block, a

second sleeve mounted-upon the shaft and extending within the first sleeve, said sleeves having screw threaded engagement with one another, a pinion carried by the second sleeve normally spaced from the first sleeve but movable axially with the second sleeve into engagement with the end of the first sleeve, and means operative during the early stages of such movement to restrain the pinion against rotation.

10. A power transmission mechanism comprising a power shaft, a central supporting shaft, a sleeve loosely mounted thereon, a yielding driving connection between the power-shaft and sleeve, and a driving member connected with the sleeve for rotary move- I ment therewith and longitudinal movement hereof, said yielding driving connection including two cooperating spring pressed cams, one of which is rigidly connected with the power shaft and the other is yieldingly connected' with the sleeve through the spring.

11. A'power transmission mechanism come prising a power shaft, a central supporting shaft, a sleeve loosely mounted thereon, a

yielding driving connection between the power shaft and sleeve, and a driving member connected with the sleeve for rotary movement therewith and longitudinal movement thereof, said yielding driving connection ineluding two cooperating spring pressed cams in the form of collars which are mounted upon the sleeve, one of the cams being rigidly connected with the power shaft and the other being'yieldingly connected with the sleeve and having a yielding longitudinal movement rel- I ative thereto.

12. A power transmission mechanism comprising a power shaft, a central supporting shaft,,a sleeve. loosely mounted thereon, a yielding driving connection between the power shaft and sleeve, and a driving member connected with the sleeve for rotary moveprising a power shaft having a yoke, a central yielding driving connection between the power shaft and sleeve, and a driving member connected with the sleeve forrotary movement therewith and longitudinal movement thereof, said yielding driving connection including two cooperating cams in the form of collars which are mounted upon the sleeve, one of the cams being connected with the power shaft and having means to prevent longitudinal displacement of the sleeve, and the other of which cams is mounted for longitudinal movement on the sleeve, and a spring connection between the sleeve and the last named cam.

14. A power transmission mechanism cemprising a power shaft, a central supportlng shaft in axial alinement therewith, a sleeve loosely mounted on such central shaft, a yielding driving connection between the power shaft and sleeve, and a driving member mounted loosely on the central shaft and having a screw threaded hub said member and its hub bearing on such central shaft as to their entire length, said sleeve having at one end a screw threaded bore to receive said hub.

- 15. A power transmission mechanism comcentral shaft, a driving member mounted on the central shaft and connected with the sleeve for rotary movement therewith and longitudinalmovement. thereof, and a yielding driving connection between the yoke and the sleeve.

16. A power transmission mechanism comprising a power shaft having a yoke, a central, supporting shaft secured to the yoke at its axis of rotation, a sleeve loosely mounted on the central sh aft, a driving member mounted on the central shaft and connected with the a sleeve for rotary. movement therewith and longitudinal movement thereof, and a yielding driving connection between the yoke and the sleeve, said driving connection including a collar connected with the yoke and having a cam face, and a spring pressed collar mount.-

ed loosely on the sleeve for longitudinal movement and having a complementary cam 17. A power transmission mechanism comsupporting shaft secured to the yoke at its axis of rotation, a sleeve loosely mounted on the central shaft, a driving member mounted on the central shaft: and connected with the sleeve for rotary movement therewith and 1ongitudinal movement thereof, and a yielding driving connection between the yoke and the sleeve, said driving connection including a collaradjusta-bly connected with the yoke and having aeam face, and a spring pressed collar mounted loosely on the sleeve forlongitudinal movement and having a complementary cam face. p v 18. A power'transmlssion mechanism comprising a power shaft having a yoke a central supporting shaft secured to the yoke at its axis of rotation, a sleeve loosely mounted on the central shaft, a driving member mounted on the central shaft and connected with the sleeve for rotary movement therewith and longitudinal movement thereof, and a yieldshaft, a driving member connected with oneend oft-he sleeve for rotary movement therewith and longitudinal movement thereof, and

a vielding driving connection between the yoke and the sleeve, said yoke extending partially over the sleeve and encompassing the end thereof.

20. An en 'ne starter drive includin a as driving mem er adapted to engage a mem er.

of an engine to be stared, a'driven shaft associated with said driving member to rotate it,

a driving element, and a combined drivingspring andclutch-structure operatively asso- I ciating said'driving element and said driven shaft for torque transmission through sald clutch and spring and comprising a clutchv held normally in engagement by the tension of said spring and adapted to be automati 85 cally de-clutched against the tension of said spring. 21. An en ine starter drive including a driving mem lier adapted to engage a member of an engineto be started, a driven shaft associated with said drivingmember to rotate-it, a driving element, and a combined driving-sprin and clutch-structure operatively associating said driving element and saiddriven shaft for torque transmission ing a clutch inherently tendin to de-clutch under tor ue and normally hefd against del clutching y tension of said spring.

the former to the latter.

through said clutch and spring and compris-' I I said sleeve having a threaded portion with a shoulder at the rear end of the threadedportion, an attaching collar mounted on and secured to the motor shaft, and a helical connecting spring between the collar and the nut.

24. An engine starter drive including a power-driven shaft, an externally-threaded 'sleeve mounted for movement, on a smooth portion of said shaft and carrying a driving member adapted for longitudinalmovement 78 to engage and rotation to crank a member of the engine to be started, an internally threaded nut member engaging said threaded sleeve, and a combined driving-spring and clutchstructure operatively associating said shaft and said sleeve for torque transmission through said clutch and spring and including a clutch held normally in engagement by tension of saidspring and adapted to be automatically declutched against the tension of said spring. 25. An engine starter drive includin a power-driven shaft, an externally-threa ed sleeve mounted for movement on a smooth portion of said shaft and carrying a driving $0 member adapted for longitudinal movement to engage and rotationto crank a member ofv the engine to be started, an internally threaded nut-member engaging a said threaded sleeve, said nut-member and sleeve having cooperative stop-provisions arranged for coaction when the driving member reaches a position for adequate engagement with the engine-member and a helical drive spring concentric with the shaft and operatively interosed between said shaft and said nut-memr to yield under torque transmission from Signed by me at Boston, Massachusetts this 8th day of May, 1922.

' ALBERT A. DENSMORE;

22. An en 'ne-starter drive includin a driving mem r adapted to engage a mem' r of an engine to be started, a driven shaft assoeiated with said driving member to rotate it, a driving element and a combined driving-spring and clutch-structure operatively associating said driving element and said driven shaftvfor torque transmission through said clutch and spring and comprising a clutch inherently tending to de-clutch under torque and having an element, movable for de-clutching, connected with said spring and normally held against de-clutching by ten-' a Sion of said s ring.

23. *In com ination, a one-piece sleeve and pinion member adapted to be mounted on a driving'shaft, a threaded nut on said sleeve,

CERTIFICATE OF CORRECTlON.

PatentNo. 1,885,342. October 18, 1932.

ALBERT A. DENSMORE.

It is hereby certified that the residence of the assignee in the above numbered patent was erroneously written and. printed in the grant and heading to the printed specification as "Elmira, New Jersey" and "Elmira Heights, New Jersey" respectively, whereas said residence should have been written and printed as Elmira Heights, New York, as shown by the records of assignments in this office; and that the said Letters Patent should be read with this correction therein that 'the same may conform to the record of the case in the Patent Office.

Signed and sealed this 25th day of February, A. D. 1936.

Leslie Frazer Acting Commissioner of'Patents. 

